BenQ EX3501R, AOC U3477PQU and a faulty DisplayPort cable (WHL #33F4)
Well, who would have thought that the BenQ needed another blog post…
Last week, the line flicker described in got significantly worse. I switched graphics cards the week before (Radeon 260X out, 380 in), which resulted in a driver reset and one Windows boot for the short sighted, but it also caused a bit of movement on the cables, as my computer is rack-mounted. Flicker stuff was the same for a few days.
Then it got so bad that it not only had those intermittent lines, but there were entire blocks of lines just black, audio stuttered, and the entire screen went dark for a second every so often. It never displayed the resolution notifier, so I guess it did not resync to the DP input, but this was part of the video stream.
Could be the new GPU as well, right? Let’s play our favourite game of exchanging piece by piece until the error goes away.
First stop: Testing the DP cable on a different machine. I don’t own a second monitor that uses DP, but there’s a similar machine at work. AOC U3477PQU 3440×1440 display (only 60 Hz, though) and a Radeon 360(X?). I had a defective cable on that one before, but the fault was obvious: Wouldn’t show anything at all. Probably the cheapest cable they were able to source, both the old one as well as the replacement.
So I unplugged it and went to work. What do you know…
(Youtube is a PAIN IN THE ASS – reading orientation data from MP4 files does work, but if you upload cropped MKVs that do not have an orientation flag, there’s no way to rotate it later. Audio removal does not work, but you can replace it with some funky public domain tunes. Dafuq…)
Using the UHD test image from DSS-4K.de , it seems like the AOC is freaking out even more, or the system at work does deliver more crap over DP than my computer at home does. So I nailed it on first try – the cable must be damaged. Let’s compare that stuff with the GIFs from last time (which I attributed to FreeSync – I very well might be wrong on that one!)
Like last time, a click on the images will lead you to the full-sized one. This time coming from SlowMo mode on my Samsung Galaxy S5…still 1920×1080 like the Canon did. I’m not a movie camera operator, you know…
Line flicker is similar – I guess I have to take the FreeSync label back. That shit was due to cabling all the time and I didn’t realize! Could have returned the cable in the first place, damn…
As mentioned, the AOC seems more susceptible to other crap. I admit I twiddled around quite a bit to induce the errors, but I couldn’t make them appear more often. It also did not change with resolution (tried a lot at home), so I’d assume this is a shielding issue. If anyone has a testing tool to e.g. disable DisplayPort streams (3440×1440@100 should utilize 4 streams, as far as I know), please let me know. Also, if you’re Agilent, Rohde & Schwarz or some other fancy company that makes equipment that is capable of snooping into the 32Gb/s of streams that DP squeezes through a cable and would like to sponsor me test equipment, please get in contact
Jokes aside, this looks like shifted content, either from the very same image or from the previous frame.
It’s quite similar each time, isn’t it?! Not sure why, the flickery lines looked random to me.
Ultimate proof that it’s a faulty cable: Buy a new one that works. So I did. After some research, the (certified) Lindy Chromo cables seem very popular, but they are ~35m€ for the 3m that I need for my rack installation. 2.5m would be okay, but they are very rare for whatever reason. Even the manufacturers claim that length is an issue, but nobody wants to offer something between 2m and 3m. An audiophile colleague recommended Oehlbach snake oil for 65€, I politely declined. Cheap cables start at like 5€, the faulty one was an Ednet brand for 8.43€. I finally decided for a certified Club 3D “CAC-1060” cable that is DP1.4 HBR3 / 8K@60 compatible. Not really needing the entire 32.4Gb/s, but unused bandwidth is better than missing bandwidth, isn’t it? The cable is pretty inconspicuous and so is the packaging. Not even gold finish on the outer DP plug. But – it works! Line flicker gone, audio stutter gone, no black lines or entire screens. It just works, and the BenQ is working just fine. A steal for 25,23€ plus pickup at a local super market (!).